This is the text of an invited review paper published in Energy Transport in Radio Galaxies and Quasars, Volume 100 in the ASP Conference Series, edited by Philip Hardee, Alan Bridle, and Anton Zensus.
For further information about this volume, consult http://www.cv.nrao.edu/~abridle/etransp.html
This HTML document is based on one generated using the LaTeX2HTML translator Version 0.6.4 (Tues Aug 30 1994) Copyright © 1993, 1994, Nikos Drakos, Computer Based Learning Unit, University of Leeds.
The translation was initiated by Alan Bridle on Wed Apr 10 10:19:46 EDT 1996